Robust, sacroiliac, anchoring in three degrees of freedom

Abstract

An anchor has a straight centerline and straight splines extending radially while running parallel thereto. Splines extend radially from a core penetrated by a channel to fit over a K-wire guide, and axially along the length of the elongate, cylindrical core. The center line passes along the center of a lumen or channel of the hollow core, while the splines extend radially outward from, and axially along the length of the core except along a conical taper near a leading or point end of the anchor. Installation may be from a posterior access or a lateral-posterior access, each anchor fixing two bones in at least one, but usually two, degrees of freedom. Multiple anchors may fix in all six degrees of freedom (three degrees of freedom in translation along three mutually orthogonal axes, and three degrees of freedom of rotation about those same axes).

1 . A method for fixing a first bone to a second bone, the method comprising:
 providing an anchor comprising a core, extending along an axis defining axial and radial directions and having a base end and a point end, and a plurality of splines, each spline extending radially away from and substantially perpendicular to the core and tapering at the point end;   providing access to two bones, each presenting a cortical surface to be joined to the other;   penetrating, by the anchor, thereby fixing each of the cortical surfaces in at least two degrees of freedom with respect to the other in response to engagement of each by the splines.   
     
     
         2 . The method of  claim 1 , wherein the core further comprises a lumen that enables guiding the anchor, and wherein the access is provided by at least one of an incision, a dilation, insertion of a guide, reaming, broaching, installing a portal, and inserting tools along a guided path. 
     
     
         3 . The method of  claim 2 , wherein the access is provided by a process including an incision, a dilation, insertion of a guide, installing a portal, and inserting tools through the portal. 
     
     
         4 . The method of  claim 2 , further comprising:
 installing multiple anchors engaging the two bones, effecting fixation with respect to one another in six degrees of freedom.   
     
     
         5 . The method of  claim 1 , wherein the two bones are a sacrum and an ilium. 
     
     
         6 . The method of  claim 5 , wherein the core further comprises a lumen that enables guiding the anchor, and wherein the access is provided by at least one of an incision, a dilation, insertion of a guide, reaming, broaching, installing a portal, and inserting tools along a guided path. 
     
     
         7 . The method of  claim 6 , wherein the access is at least one of a posterior access and a lateral-posterior access. 
     
     
         8 . The method of  claim 7 , wherein the posterior superior iliac spine (PSIS) is used as a landmark. 
     
     
         9 . The method of  claim 7 , wherein the anchor crosses the cortical surfaces in a direction principally orthogonal to both cortical surfaces, and further comprising:
 providing a second anchor comprising a second core, extending along an axis defining axial and radial directions and having a second base end and a second point end, and a second plurality of splines, each spline extending radially away from and substantially perpendicular to the second core and tapering at the second point end; and   penetrating, by the second anchor, along a joint region between the cortical surfaces principally parallel to both cortical surfaces.   
     
     
         10 . A method for fixing a first bone to a second bone, the bones each comprising a cortical portion and a medullar portion, the method comprising:
 selecting an anchor comprising a core, hollow inside with a plurality of splines on an outside surface, the core extending along an axis, the axis defining axial and radial directions with respect thereto, and each one of the plurality of splines extending radially away from, and substantially perpendicular to, the core;   providing access to two bones, wherein the two bones are a sacrum and an ilium, each presenting a cortical surface to be joined to the cortical surface of the other;   penetrating, by the anchor, fixing each of the cortical surfaces in at least one degree of freedom with respect to the other.   
     
     
         11 . The method of  claim 10 , further comprising:
 inserting a Jamshidi needle into flesh a distance to reach a first bone;   removing a trocar from within the Jamshidi needle;   inserting a guide of k-wire through the Jamshidi needle;   removing the Jamshidi Needle;   inserting through the flesh and along the guide a first dilator;   inserting through the flesh a second dilator having an inner diameter larger than an outer diameter of the first dilator;   inserting through the flesh and anchoring into at least one of the first and second bones a working portal having an inner diameter larger than an outer diameter of the second dilator;   removing the dilators;   determining a distance into the working portal;   creating a path by piloting a selected distance beyond the working portal; and   fixing the first bone with respect to the second bone in at least two degrees of freedom by engaging the first and second bones by the splines of the anchor due to inserting the anchor along the path.   
     
     
         12 . The method of  claim 10 , wherein the core further comprises a lumen that enables guiding the anchor, and wherein the access is provided by at least one of an incision, a dilation, insertion of a guide, reaming, broaching, installing a portal, and inserting tools along a guided path. 
     
     
         13 . The method of  claim 12 , wherein the access is at least one of a posterior access and a lateral-posterior access. 
     
     
         14 . The method of  claim 11 , wherein the splines are buttressed and the material of the anchor is selected from the group consisting of: a metal, a polymer, a reinforced polymer, and a bone. 
     
     
         15 . An apparatus comprising:
 a core having a base end and a point end;   a plurality of splines;   the base end and the point end each lying along a central axis defining a radial direction, proceeding orthogonally away therefrom; and   the splines extending between the base end and the point end, each extending radially away from the central axis.   
     
     
         16 . The apparatus of  claim 15 , wherein the point end is selected from a solid point, constituted by a convergence of the splines at a corresponding narrowing of a diameter of the core, and a hollow point, constituted by a tubular core from which the splines extend radially. 
     
     
         17 . The apparatus of  claim 16 , wherein the splines further comprise barbs and the material of the anchor is selected from the group consisting of: a metal, a polymer, a reinforced polymer, and a bone. 
     
     
         18 . The apparatus of  claim 16 , wherein the anchor further comprises at least one grow-through space and the material of the anchor is selected from the group consisting of: an allograft, a homograft, and an autograft. 
     
     
         19 . The apparatus of  claim 16 , wherein the core is tapered, having a circumference that is greater at the base end as compared to the point end. 
     
     
         20 . The apparatus of  claim 16 , further comprising a frame provided with anchor apertures capable of receiving and guiding a plurality of the anchors in directions capable of securing multiple bones to the frame and effecting through-growth between the multiple bones through the frame.